J. Am. Chem. SOC.1982, 104, 4285-4286 for the NMR spectra. This work was supported by Grant AI 18362 from the National Institute of Allergy and Infectious Diseases. The National Science Foundation (PCM 79- 12083) and the Dreyfus Foundation supported the 7 T Nicolet NMR spectrometer, and the National Institutes of Health (RR 00862) supported the Mass Spectrometric Biotechnology Research Resource.
4285 14’
F[!I
Registry No. 4, 82136-16-1; 5, 82136-17-2; 6, 82136-18-3; 7, 8213619-4; 8, 82136-20-7; 9, 82136-21-8; BOC-Cys(4-MeC6H4CHz)-OH, 61925-77-7; H-Gly-OMe, 616-34-2; MeCO-Gly-OH, 543-24-8; Cys(4CH3Bzl)-Gly-OCH3,82136-22-9; BOC-Gln-OC6H4N0z-4, 15387-45-8; Asn-NH-CH3, 821 36-23-0; Gln-Asn-NH-CH3, 82136-24-1; Boc-Glu(OBzl), 13574-13-5.
Homo- and Heterodinuclear Platinum and Palladium Complexes with a Single Unsupported Monoatomic Bridging Group. Crystal Structure of the 2,6-Bis[ (dimethylamino)methyl]phenylpalladium(II) Derivative [ (Pd{C6H3(CHzNMez)2-o ,o’))z(p-Cl)]BF4 David M. Grove, Gerard van Koten,* and Henk J. C. Ubbels Anorganisch Chemisch Laboratorium J. H . van? Hoff Instituut, University of Amsterdam 1018 WV Amsterdam, The Netherlands
Figure 1. PLUTO drawing along with the adopted numbering scheme. Important distances (A) are Pd(1)-Cl(1) = 2.463 ( l ) , Pd(1)-N(l) = 2.105 (3), Pd(1)-N(2) = 2.100 (4), Pd(1)-C(9) = 1.929 (4), Pd(2)Cl(1) = 2.458 ( l ) , Pd(2)-N(3) = 2.094 (3), Pd(2)-N(4) = 2.104 (3), and Pd(2)-C(21) = 1.909 (4). Some relevant angles ( O ) are Cl(l)-Pd(1)-N(l) = 97.0 (l), Cl(l)-Pd(l)-N(2) = 100.3 (l), Cl(l)-Pd(l)-C(9) = 174.5 (l), N(1)-Pd(1)-N(2) = 162.6 ( l ) , Cl(l)-Pd(2)-N(3) =$J7.9 (l), Cl(l)-Pd(2)-N(4) = 97.6 (l), Cl(l)-Pd(2)-C(21) = 174.3 (l), and N(3)-Pd(2)-N(4) = 164.3 (1). Scheme I
M-
Anthony L. Spek
X
Laboratorium voor Struktuurchemie, Rijksuniuersiteit 3584 CH Utrecht, The Netherlands Received March 15, 1982
’
10,M = M ‘ = P d . X = C l
ZZBF4
There are few dinuclear complexes of the nickel triad metals I \N %” le, M = P d M‘ZPt X Z B r in which the metals are only bridged by a single atom. It was only recently, for example, that IPh(PEt~)2Pt(~-H)Pt(PEt3)2Hl+, containing a single hydride bridge between two Pt(I1) centers, was structurally characterized. * We now report the first examples of homo- and heterodinuclear Pd(I1) and Pt(I1) complexes possessing a single unsupported chloro, bromo, or iodo bridge. The successful synthesis of these complexes (see Scheme I) involves the use of the terdentate anionic Me2N ligand ( O , O ’ - ( M ~ ~ N C H ~ )(N-C-N) ~ C ~ H ~ )which, as a result of its special attachment, produces square-planar [M(N-CN)(H20)]+ (M = Pd, Pt) species with a loosely bound H 2 0 molecule in a site trans to a 0 M-C bond. Displacement of this H2 2PPh3 good leaving group ( H 2 0 ) by a terminal halide of a neutral M-S z-P I (C0D)? [M’(N-C-N)X] complex then leads to formation of the new - H20 1. This dinuclear species [ (N-C-N)M’(pX)M(N-C-N)]+, Lewis acid-base pairing reaction2carried out at room temperature in CH2Clzaffords these air-stable products in virtually quantitative S= H20 30,M:Pd 3b,M;Pl Z=BF, yield upon evaporation of the s01vent.~ The proposal for 1 of a dinuclear ionic formulation was based on IR$ NMR (vide infra), The cation (see Figure 1) as anticipated consists of two and analytical data and is in accord with the observation that the ~~~~S-N,N’,C-[P~[C~H~(CH~NM~~)~]] units sharing a single complexes are readily soluble in polar solvents (e.g., CH2C12). bridging chlorine atom. Both Pd(I1) centers have a slightly To firmly establish the presence of only a single halo atom distorted square-planar coordination sphere (e.g., N( 1)-Pd( 1)bridge, we have completed a single-crystal X-ray structure determination on one representative member, l a (M = M‘ = Pd, (5) Pale yellow X-ray analysis crystals of la, C 4H3,ClN4Pd2.BF4,were x = c1).5 monoclinic space group P2,/c with a = 11.163 (1) b = 21.347 (2) A, c = 12.246 (4) A, fl = 91.48 (Z)”,2 = 4, ddd = 1.634 g/cm3. The intensity data
L
0
[@q
A,
(1) Bracher, G.; Grove, D. M.; Venanzi, L. M.; Bachechi, F.; Mura, P.; Zambonelli, L. Angew. Chem., Int. Ed. Engl. 1978, 17, 778-779; Angew. Chem. 1978, 90, 826-827. (2) For background information see: “Hard and Soft Acids and Bases”; Pearson, R.G., Ed.; Dowden, Hutchinson and Ross: Stroudsburg, PA, 1973. (3) Although a dinuclear species is not isolated when [Ni(N-C-N)X] is included in this reaction scheme, the resultant formation of [Ni(N-CN)H20]+ strongly suggests the presence of such a Ni(I1)-containing complex as the reactive intermediate. (4) yap 1080 cm-I, no identifiable v M or ~ uM,~.
0002-7863/82/1504-4285$01.25/0
were measured on a Nonius-Enraf CAD4 diffractometer (Zr-filtered Mo Ka radiation) with C28 scans. A total of 6691 unique reflections were measured for 8 < 27.5O of which 5077 were considered observed [I < 2,5u(l)]. The structure was solved by standard Patterson and Fourier techniques and refined by blocked full-matrix least-squares methods. In the final refinement hydrogen atoms were refined in a riding mode with a rotation parameter for the rigid methyl groups. There is some disorder in the BF4 anion and the ligand on Pd(2) (two equivalent, mirror plane related puckering possibilities),both of which have the same occupation parameters (84:16). Final refinement converged at RF = 0.042 and R w p = 0.048. Figure 1 and the data apply to the 84% molecule.
0 1982 American Chemical Society
4286
J. Am. Chem. Soc. 1982, 104, 4286-4288
N(2), 162.6 (1)'; C(g)-Pd(l)-Cl, 174.5 (l)', and the two virtually The present results emphasize that for mononuclear complexes equivalent coordination planes are orientated almost perpendicular of the nickel triad Lewis acid-base pairing, via either a halide to each other (88.5 (2)0).6 The Pd(l)-Cl-Pd(2) angle of 134.8 or hydride ligand, is readily attained, and therefore it may play (1)' is a dominant structural feature, which taken with the two an important role in the reaction mechanisms of ligand substitution fairly long Pd-CI distances (2.463 (1) and 2.458 (1) A) gives rise and exchange. It is worth noting that the terdentate ligand (Nto a Pd-Pd separation (4.544 (2) A) that is much greater than C-N) has enabled the isolation of [(N-C-N)Pt(p-RNCHNR)that found in complexes where there is a distinct M-M bond.7 AgX] species16containing a direct Ag-Pt interaction, and further The large deviation of this angle from that expected for a tetraresearch in this laboratory is being directed to a better underhedral halide atom (two bonds, two long pairs; cf. isoelectronic standing of this ligand's role in stabilizing heteronuclear complexes. [(C5H5)(CO)2Fe(r-I)Fe(C0)2(C5H5)], LFe-I-Fe = 110.8 (1)")* Acknowledgment. Professor K. Vrieze and Professor L. M. is presumably steric in origin. Venanzi are thanked for helpful discussions. This investigation The solution 'H N M R data of l a [60 MHz; CD2C12;6 CH2 was supported in part by the Netherlands Foundation for Chemical 4.03, CH3 2.951 evidences retention of both the Lewis acid-base Research (SON), with financial aid from the Netherlands Orinteraction and coordination of the N donor ligands on the N M R ganization for Pure Research (ZWO) (A.L.S.) time scale.g Since in the solid-state structure there are not only inequivalent CH2NMe2groupings but also diastereotopic CHI Registry No. la, 82112-75-2; l b , 82112-77-4; IC, 82112-79-6; Id, and Me groups, the N M R solution observation of only single CH2 82112-81-0; le, 82112-83-2; 2, 82112-85-4; 3a, 82112-87-6; 3b, 82112and CH3signals means that there is a fluxional process, most likely 89-8; Pt(NCN)(CF$OJ, 821 12-90-1; Pt(NCN)(COOH), 821 12-91-2; a rotation about the metal-halogen axes, that renders the [Pt(NCN)(H,O)] BF4, 82 1 12-93-4; [Pt(NCN)(H,O)] BF4, 82 1 12-95-6; Pt(NCN)Cl, 821 12-96-7; Pt(NCN)Br, 67507-09-9; Pt(NCN)I, 821 12CH2NMe2environments equivalent. The 'H N M R data for the 97-8; Pd(NCN)Cl, 821 12-98-9; Pt(COD),, 12130-66-4. other dinuclear species lb-e are similar. There is also N M R evidence for a further fluxional processlo involving a fast reversible Supplementary Material Available: Tables of positional and dissociation of the dinuclear units initiated by traces of water (a BF, thermal parameters for [ (Pd(C6H3(CH2NMe2)2-o,01)2(p-Cl)] weak coordinating ligand). and of bond distances and bond angles ( 5 pages). Ordering Complexes la-e are, as far as we are aware, the first structurally information is given on any current masthead page. characterized species in which a single halide bridge atom binds two nickel triad metal centers without the support of bidentate (15) Bracher, G.; Grove, D. M.; Pregosin, P. S.;Venanzi, L. M. Angew. phosphine or arsine ligands as found in, for example, A-frame Chem.. Int. Ed. End. 1979.18. 155-156: Anpew. Chem. 1979.91. 169-170. complexes." (16) Van der Pl&g, A. F. M. J.; van Kot&, G.; Vrieze, K.'Inorg. Chem. To investigate the versatility of the [M(N-C-N)]+ system to 1982,21, 2026. act as a Lewis acid, we have extended our interest to hydridecontaining species (see scheme). From the reaction of [Pt(NC-N)(CF,SO,)] and [Pt(N-C-N)(COOH)]I2 in benzene at 50 OC was isolated the monohydrogen bridge complex [(N-C-N)Pt&-H)Pt(N-C-N)]', 2,13in almost quantitative yield ['H N M R Multiplet Selection in Crowded 'H NMR Spectra via (CD2C12)6 -4.54 (Pt,H,Pt), J(Pt,H) = 576 Hz]. This is the first Double Quantum Coherence complex containing N donor ligands that has a structural relationship to the unique dihydride [Ph(PEt3)2Pt(p-H)Pt(PEt3)2H]+,' P. J. Hore, E. R. P. Zuiderweg, K. Nicolay, K. Dijkstra, and which also contains a three-center two-electron M-H-M bridge R. Kaptein* bond. It is also possible to synthesize dihydride-bridged complexes Department of Physical Chemistry [N-C-N)M(pH),Pt(PPh,),1+ (M = Pd (3a), Pt (3b)) by using University of Groningen a procedure in which a reactive hydride is generated in situ from 9747 AG Groningen, The Netherlands the reaction of Pt(0) phosphine species and gaseous H2. From Received March 25, 1982 spectroscopic data ['H N M R (acetone-d6) 6 (3a) -3.84 ( P - H ) ~ , J(Pt,H) = 818 Hz); (3b) -1.86 (p-H)2, J(Pt,,H) = 707 Hz, We propose a new method for tackling a perennial problem in J(PtB,H) = 385 Hz],', these complexes are anticipated to have N M R spectroscopy, that of spectral overcrowding. It allows one a geometry in which there is both a four- and a five-coordinate to detect specific multiplet resonances in circumstances where they center, a situation also existing in the related tertiary phosphine would be partially or totally obscured by line overlap in a conspecies [(PR3)2Pt(p-H)2Pt(PR3)2H]BF4 (R = Ph, Cy, Et).I5 ventional 'H N M R spectrum. All that is required is prior knowledge of the approximate chemical shifts and J couplings of the protons of interest. (6) Calculated from the least-squares planes of the carbon atoms of the two phenyl moieties. Our approach was inspired by recent experiments',2 for ob(7) In [Pd2(Ph2PCH2PPh2),Br2] the M-M separation is only 2.699 (5) A: serving 13C-13C spin-spin coupling in natural-abundance I3C Holloway, R. G.; Penfold, B. R.; Colton, R.; McCormick, M. J. Chem. Soc., N M R spectra. The method, known as INADEQUATE,^^ relies on Chem. Commun. 1976,485-486. the momentary creation of double quantum coherence between (8) Cotton, F. A.; Frenz, B. A.; White, A. J. J . Orgunomef. Chem. 1973, 60, 147-152. coupled I3C nuclei to suppress the strong signals from molecules (9) N donor coordination to palladium centers is established from 'H with an isolated 13C. INADEQUATE was later extended into a NMR shift data, but for platinum species this is subtantiated by the presence two-dimensional Fourier transform e ~ p e r i m e n tfor ~ ?correlating ~ of 195Ptcouplings with the CH2NMe, signals. (10) Mixing [Pt(N-C-N)Br] with [Pt(N-C-N)(H20)]BF4 in CH2Cl1 at room temperature in ratios other than 1:l gives rise to only one CH2NMe2 'H NMR resonance pattern (with 195Ptsatellites). (1 1) The geometric constraints of bridging bidentate ligands can have a significant influence on the geometry of A-frame complexes. The structure shows a Pd-I-Pd angle of 67.0 (1) of [Pd2(Ph,PCH,PPh2)2(p-I)(CH3)I]BF4 A: Olmstead, M. M.; Farr, J. P.; Balch, A. L. Inorg. Chim. Acta 1981,52, 47-54. (12) Synthesized from [Pt(N-C-N)(H20)]BF4 and NaCOOH in H 2 0 at room temperature (IH NMR (benzene-d6)6 9.78 (COOH, J(Pt,H) = 52 Hz). (13) The synthesis of a terminal Pt-H bond by thermal elimination of C 0 2 from a Pt(CO0H) group has been documented. See for example: Catellani, M.; Halpern, J. Inorg. Chem. 1980,19,566-568. (14) FA !s bound to the two PPhl groups. The satellites arising from PtB are significantly broadened owing to incomplete collapse of spinspin coupling of Is5Pt to the I4N doqor atoms.
0002-7863/82/1504-4286$01.25/0
(1) Bax, A.; Freeman, R.; Kempsell, S.P. J . Am. Chem. SOC.1980,102, 4849. (2) Bax, A. Doctoral Thesis, Technische Hogeschool Delft, The Netherlands, 1981. (3) Richarz, R.; Ammann, W.; Wirthlin, T. J . Mugn. Reson. 1981,45,270. (4) Serrensen, 0. W.; Freeman, R.; Frenkiel, T.; Mareci, T. H.; Schuck, R. J. Mugn. Reson. 1982,46, 180. (5) Bax, A.; Freeman, R.; Frenkiel, T. A. J . Am. Chem. SOC.1981,103, 2102. (6) Bax, A,; Freeman, R.; Frenkiel, T. A,; Levitt, M. H. J. Mugn. Reson. 1981,43, 478. (7) Aue, W. P.; Bartholdi, E.; Ernst, R. R. J. Chem. Phys. 1916,64, 2229. (8) Equation 3 and the cosine part of eq 2 are also valid for strong coupling.'
0 1982 American Chemical Society
